It is known in the priot art to provide a failsafe optically coupled logic function apparatus, as shown by U.S. Pat. No. 3,826,930 of R. H. Perry, which can perform the AND, the OR, the latching and the signal transfer function. For the failsafe control of mass transit vehicles, this optically coupled failsafe logic function apparatus performs the same logic functions that were previously performed by vital relays. A light emitting diode device is energized to emit light in response to the concurrent provision of a first logic control signal in conjunction with the presence of a second input signal.
It is known in the prior art to provide a failsafe logic apparatus having an input module including a light emitting diode and an output module including a light responsive active circuit means, as shown by U.S. Pat. No. 3,995,173 of H. C. Sibley.